It is desirable to increase the resistance of zeolite Beta based catalysts to steam, thermal and liquid phase hydrolytic catalytic deactivation. The benefits afforded by the increased stability of zeolite Beta based catalysts due to application of this invention could have immediate impact in the development of improved fluid cracking catalysts.
Zeolite Beta and its preparation are taught in U.S. Pat. No. 3,308,069 (Re. 28,341). U.S. Pat. No. 4,642,226 teaches a method for synthesizing crystals having the structure of zeolite Beta from a reaction mixture comprising dibenzyldimethylammonium ions as directing agent, and the crystals synthesized thereby. Highly silicious zeolite Beta described as having silica-to-alumina ratios within the range of 20-1,000 is disclosed in U.S. Pat. No. 4,923,690. U.S. Pat. No. 5,164,170 discloses a method for synthesizing large crystal size zeolite Beta from a reaction mixture using a directing agent comprising tetraethylammonium compound and including triethanolamine, and the crystals synthesized thereby. U.S. Pat. No. 5,232,579 discloses a method for synthesis of Zeolite Beta using a chelating agent. Zeolite Beta is characterized by a distinctive X-ray pattern which distinguishes it from other known crystalline silicates. The entire contents of the above disclosures are incorporated herein by reference as to description of the zeolite Beta structure and synthesis.
The X-ray diffraction pattern of the crystalline silicate identified as zeolite Beta is shown in U.S. Pat. No. 3,308,069, herein incorporated by reference. It is indicated in U.S. Pat. No. 3,308,069 that appearance and disappearance of certain X-ray lines can be attributed to compositional differences in silicon to aluminum ratios in the sodium form compositions summarized in Table 2 of that reference with interplanar d-spacing (Angstroms) given in terms of intensity for several dried samples of zeolite Beta. Table 3 of U.S. Pat. No. 3,308,069 again shows X-ray diffraction lines for zeolite Beta with certain variations in intensities and line appearance attributed to cation exchange of zeolite Beta. The more significant d-spacing values for exchanged zeolite Beta appear in Table 4 of U.S. Pat. No. 3,308,069 and are as follows:
______________________________________ Interplanar d-Spacing (.ANG.) ______________________________________ 11.4 .+-. 0.2 7.4 .+-. 0.2 6.7 .+-. 0.2 4.25 .+-. 0.1 3.97 .+-. 0.1 3.0 .+-. 0.1 2.2 .+-. 0.1 ______________________________________
U.S. Pat. No. 4,642,226, incorporated by reference herein, discloses characteristic X-ray diffraction lines as determined by standard techniques and as shown in Table I.
TABLE I ______________________________________ Interplanar d-Spacing (.ANG.) Relative Intensity (I/I.sub.o) ______________________________________ 11.5 .+-. 0.3 M-S 7.4 .+-. 0.2 W 6.6 .+-. 0.15 W 4.15 .+-. 0.1 W 3.97 .+-. 0.1 VS 3.0 .+-. 0.07 W 2.05 .+-. 0.05 W ______________________________________
Cracking catalysts for use in petroleum processing generally consist of a zeolitic component and a matrix. The zeolitic material is generally dispersed in an inorganic oxide-type sol or gel matrix material to which one or more clays are added. Because of the need for higher octane gasoline, there has been an emphasis on octane-increasing improvements in cracking catalysts. Octane-enhancing zeolitic fluid cracking catalysts have been reviewed recently by Scherzer, Catal. Rev. Sci. Eng., 31 (3), 215-354 (1989). The matrix components described in the article include natural or modified clays and inorganic oxides such as silica, alumina, silica-alumina, and silica-magnesia. Other inorganic oxides described for matrices are TiO.sub.2, ZrO.sub.2, P.sub.2 O.sub.5, and B.sub.2 O.sub.3.
Cracking catalysts comprising a zeolite and a matrix material containing aluminum phosphate have been described, for example, in U.S. Pat. Nos. 4,873,211 and 4,228,036. Such catalysts comprising a zeolite and an inorganic oxide matrix which contains phosphorus-treated alumina particles are described in U.S. Pat. Nos. 4,567,152 and 4,584,091 and in European Patent Applications 176,150 and 403,141. The treatment of zeolite catalysts with phosphoric acid to provide a phosphorus-containing catalyst is described in U.S. Pat. No. 4,839,319 and 4,498,975.
In U.S. Pat. No. 4,430,199, tricresyl or ammonium hydrogen phosphate is impregnated into a cracking catalyst to improve the tolerance toward poisoning metals. In addition, boron may be added as a passivating agent.
U.S. Pat. No. 5,110,776 discloses a method for preparing FCC catalysts comprising modifying the zeolite, e.g., ZSM-5, with phosphorus. U.S. Pat. No. 5,126,298 discloses manufacture of an FCC catalyst comprising zeolite, e.g., ZSM-5, clay, and phosphorus. Phosphorus treatment has been used on faujasite-based cracking catalysts for metals passivation (see U.S. Pat. Nos. 4,970,183 and 4,430,199); reducing coke make (see U.S. Pat. Nos. 4,567,152; 4,584,091; and 5,082,815); increasing activity (see U.S. Pat. Nos. 4,454,241 and 4,498,975); increasing gasoline selectivity (see U.S. Pat. No. 4,970,183); and increasing steam stability (see U.S. Pat. Nos. 4,765,884 and 4,873,211).
Phosphorus treatment has also been used on zeolite Beta type catalysts (see U.S. Pat. Nos. 5,232,579; 5,231,064; 5,194,412; 5,190,902; 5,179,054; 5,126,298; 4,724,066; and 4,605,637).
As mentioned above, it is desirable to increase the resistance of zeolite Beta based catalysts to steam, thermal, and liquid phase hydrolytic catalytic deactivation. The benefits afforded by application of this invention could have immediate impact in the development of improved fluid cracking catalysts. Other applications where more stable, phosphorus containing zeolite Beta catalysts with higher alpha activities could be of use (e.g., NiMo containing hydrocracking catalysts) are also contemplated.